The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
During processing of substrates such as semiconductor wafers, one or more film layers are deposited on the substrates. After deposition, the layers may be patterned. During some patterning steps, a hard mask layer may be used to protect selected portions of underlying layers. After processing is complete, the hard mask layer is removed using a stripping process.
Due to shrinking feature sizes, more resilient hard mask materials are being used to protect the underlying layers. For example, boron doped carbon (BDC) hard mask layers are being used. As doping levels of boron in the hard mask layers increase, the hard mask layers become more effective at protecting the underlying layers. However, the hard mask layers also become more difficult to remove using typical plasma strip processes. Therefore, the benefits of the more resilient hard mask layers are offset by damage to the substrate that occurs when the resilient hard mask layers are removed. For example, the hard mask layers may need to be removed using aggressive strip processes using fluorine chemistry. The stripping process used to remove the hard mask layers also needs to have high selectivity to materials used in the underlying layers to prevent substrate damage.